Common Denominators

Lesson Plan - Get It!

Audio:

Adding and subtracting fractions may get your heart racing, but there is nothing to fear!

You will learn how to add and subtract fractions that have a common denominator. Common denominator just means that the two fractions you are adding or subtracting have the same exact denominator.

By the end of this lesson, you will love adding and subtracting fractions!

Let's imagine you have a garden in your backyard. Every spring, tulips and daffodils begin to pop up out of the ground.

On a sunny spring day, you go outside with a ruler to measure how tall the new plants have grown so far. The tulips are ⁷/₁₆ inches out of the ground. The daffodils are only ³/₁₆ out of the ground:

• How many inches have the tulips and the daffodils grown in total?

To solve this problem, we will add the fractions.

Since both fractions share a common denominator, you are ready to add!

First, make sure our addition problem is lined up correctly. The numerators need to be in line horizontally, and the denominators need to be in line horizontally:

Now, simply add the numerators. Next, put that number as the numerator in the answer:

Finally, since you have common denominators, just move over the same denominator to your answer:

Great! The flowers have grown ¹⁰/₁₆ inches in total!

Before we move on, let's check to make sure our answer is in simplest form.

To review simplest form, go through the Study Jams! Step By Step for Simplest Form.

To make ¹⁰/₁₆ into simplest form, we will divide the numerator and denominator by 2.

So, the flowers have grown ⁵/₈ inches in total!

Now, you are ready for some practice! Visit the Got It? section to show off your skills.